Thank you, I did actually know this but I forgot.

But it only works if a select the audio clips, it doesn't apply to the entire audio track. And it of course only applies to stereo files.

If I have a mono file then these items are grayed out.

The first part of the question still stands - how do I "fill" the audio track with the wave so that the wave fills up the entire track vertically?

You can use NORMALIZE but that actually affects the audio level as well. The Waveform is showing its intensity relative to maximum levels. If you don't mind increasing the level, use NORMALIZE.

You can make the audio track larger by dragging the of the track header downward. However If the files amplitude is low, it will not make the waveform larger (louder), so confirm that normalize is enabled and set to -0.1 dBFS (Right-click the audio event, select Properties and check-mark the Normalize box). However VP uses peak normalize, so if there is one loud peak in the event, the amplitude may not be increased by much or at all. In that case, you could add an appropriate volume envelope or use a peak limiter/maximizer like Sound Forge's WaveHammer or the free LoudMax VST plug-in. Then render that audio to a new track.. in the Tools menu.

»Is there a way to alter the display in this way to be more "audio-centric"?«

As a global setting which then affects all audio tracks: Yes.

Shift+Arrow Up will zoom-in your track waveform display.

Thank you, Marco, this is exactly what I was looking for.

(Dot and Maud: I didn't want to alter the audio itself - just increase the wave display. I didn't think to use the term "zoom in". Increasing the track size does make the entire wave look bigger, but at the expense of valuable screen real estate, and I try to keep all my tracks visible without having to scroll up & down. In fact, the audio track needn't be wide at all, one just has to see enough of the waveform as a visual guide to sync'ing the video clips above.)